They're more than man's best friends: They're friends with benefits. Here are a few ways dogs are helping to make our lives healthier, safer and longer.

Search and rescue: When disaster strikes, search-and-rescue dogs are never far behind. After the Sept. 11, 2001, terrorist attacks, for example, the canine contingent in search-and-rescue efforts at the World Trade Center and the Pentagon numbered more than 350.

"A dog needs enough drive to go out on his own and find a person," says long-time dog trainer Pluis Davern. "But if I say, 'Stop — come back to me,' he has to do that too." Davern is the lead trainer for the National Disaster Search Dog Foundation, which rescues dogs from shelters, turns them into Federal Emergency Management Agency-certified search-and-rescue dogs at her Sundowner Training Kennels in Gilroy, Calif., and then gives them to first responders, mostly firefighters.

During training, Davern rewards dogs not with treats but with games of tug of war. In practice situations, she says, the dogs are looking for the person who's going to play with them. In real-life situations, "they're not rescuing people," she adds. "They just have an over-the-top desire to find the person they think has the toy."

Cancer sniffing: The same nifty sniffers that can be trained to find a person under a pile of rubble can be trained to catch a whiff of cancer in a person's breath or stool. In a study published in January, a carefully trained Labrador retriever checked out samples from more than 300 volunteers in Japan, of whom 48 were known to have colorectal cancer. The dog was accurate 95% of the time in identifying the cancer patients from breath samples and 98% of the time from stool samples. In earlier studies, trained dogs have been able to nose out bladder, lung, breast and ovarian cancer as well as melanoma.

From a practical standpoint, it seems unlikely that canine cancer screeners will ever come into widespread use. It takes a lot of time and effort to get even one dog's sniffing up to snuff. Instead, researchers hope to figure out just what it is that dogs detect and then develop a machine that can detect it too.

Cancer research: Dogs can not only help diagnose cancer, they may someday help cure it. Many scientists see the study of cancer in dogs as a promising way to learn about cancer in people. In fact, the National Cancer Institute has a Comparative Oncology Program that promotes interchanges between canine and human cancer research.

Dogs are better models for study than mice (the most typical research models) since they're closer to our size and unfortunately, like us, they develop tumors naturally all too often. (In mice, researchers have to make the tumors grow.) Besides, very often the cancers in both people and dogs share a similar biology and behavior, and respond the same way to conventional treatment.

Precisely because it may pay off for humans, more cancer research is being done in dogs. But it can pay off for dogs too — making it a win-win for both species. The research is only done with pet dogs who have already been diagnosed with cancer, and people often choose to enroll their dogs in a study because standard treatments have failed, so the experimental treatment represents one last chance to save the dog's life. Sometimes it works. And even when it doesn't, people can take comfort in knowing that what scientists are learning may help other dogs — and other people — down the road.

Predicting earthquakes: Dogs can hear things we don't hear and smell things we don't smell. But can they also sense things we don't sense that tell them an earthquake is coming? That theory has been around for more than 2,000 years. Hard evidence for it is a little shaky, though.

A study published in 1988 tested one version of the theory, namely, that more dogs run away from home just before an earthquake than at other time. But the author found no correlation between the nearly 42,000 daily reports of missing pets in the San Jose Mercury News between Jan. 1, 1983, and Dec. 31, 1985, and the 224 earthquakes of magnitude 2.5 or greater in that area during the same time period.

In 2003, a Japanese researcher had better luck connecting dog-related complaints (for excessive barking, biting, etc.) with the magnitude-7.2 Kobe earthquake in 1995. He found from public records that complaints in parts of Japan affected by the quake rose by about 18% during the two months before and after the quake. On the island right above the epicenter, complaints were up 60% in the month before the quake compared with the same month a year before.

Of course, just about every earthquake of any size at all triggers a spate of reports about pets acting weird before it hit: "My dog jumped into my lap and started licking my face for no reason." Scientists aren't impressed. They say if the earthquake hadn't happened, people probably wouldn't have given the behavior a second thought.

Besides, suppose your dog really can sense an earthquake coming and that makes her jump into your lap and start licking your face. Unless she only jumps into your lap and starts licking your face right before an earthquake, and never at any other time, you'll have a hard time knowing whether to hide under your desk when she does it.